Zinc oxide particles are widely used as filler particles in the fields such as resins, coating compositions, and greases. Such zinc oxide particles being as the filler particles are expected to have various functions. As one of features of the zinc oxide particles, there is the high conductive property.
The high conductive property causes no particular problem according to the application, but there is a difficult purpose to use the zinc oxide particles as the filler because the conductive property causes adverse effect on the use as the filler. It's often the case that the conductive property brings undesirable consequence especially in the fields of electronic materials and electronic products. Therefore, zinc oxide particles with suppressed the conductive property are expected.
As the zinc oxide particles with suppressed the conductive property, the particles disclosed in Patent Document 1 are known. Patent Document 1 discloses the zinc oxide powder of which outer periphery is modified to a high-resistivity layer by doping with the use of a monovalent dopant.
Patent Document 2 discloses zinc oxide particles suitable for the purpose as a varistor powder, and that various metals are added in definite proportion. However, concerning the zinc oxide particles disclosed in the document, the use as the varistor powder is disclosed not the use as the filler. Furthermore, the document discloses that other metals may be added but it is not able to suppress the conductive property sufficiently because aluminum is used as an essential component so that the insulation property is likely to foe reduced. That is, a career which carries an electric charge of ZnO is a free electron, and shows N-type semiconductor character. It is thought that the conductive property may be increased because Al3+ acts as a donor which gives a free electron to Zn2+ to increase the free electrons of ZnO when Al3+ is added to ZnO.
Patent Document 3 discloses an orientational zinc oxide-based piezoelectric material. However, the zinc oxide disclosed in Patent Document 3 is a zinc oxide being the piezoelectric material, there is no description about the use as the filler.